Human growth hormone (HGH) is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration. HGH is naturally produced by the pituitary gland, but synthetic versions are used by some athletes and bodybuilders to try to increase muscle mass and performance.
The effects of HGH on muscle growth are controversial. Some key points in the debate:
- Several studies have shown that giving synthetic HGH injections to healthy adults who exercise can lead to increases in lean body mass, which includes muscle. In one study, men who received HGH gained an average of 4.6 pounds (2.1 kg) of lean body mass over 12 weeks compared to no gain in the placebo group.
- However, most of these studies used high, supra-physiological doses of HGH. The muscle-building effects may not apply to more typical doses used by athletes and bodybuilders.
- The quality of the new muscle tissue produced under high HGH doses has been questioned. Some reseachers describe it as abnormal looking and unlikely to have the same strength and function as natural muscle tissue.
- Many athletes and bodybuilders use HGH along with other performance-enhancing drugs like anabolic steroids. So it's unclear how much of their muscle gains can actually be attributed to HGH itself.
- Genetics likely plays a key role in determining the skeletal muscle response to HGH. People with certain genetic variations may be "low responders" and not experience significant muscle changes from HGH.
In summary, HGH at very high, synthetic doses seems capable of increasing muscle mass when combined with exercise. However, the following factors should be considered:
- The doses required are probably too high to be practical or safe for bodybuilding purposes
- Many athletes and bodybuilders use other illegal substances in combination with HGH
- Genetics influences the skeletal muscle response
- The new tissue may not actually resemble functional muscle